Such a device is known from DE 36 04 955 C2. The known device is an x-ray diagnostic device which features a moveable C-arm on the ends of which an x-ray detector and an x-ray emitter respectively are mounted. The C-arm can be moved in relation to the support table for the patient to be examined. The movement of the C-arm is monitored with potentiometers and limit switches. The analog measurement signals delivered by the potentiometers are converted with the aid of analog-digital converters into digital values and passed to a microcomputer, which determines the current position of the C-arm from these values and checks whether the C-arm or the components mounted on it are touching a fictitious envelope surface stretched over the support table. In this case an acoustic or optical warning signal is generated. This indicates to the user, who is controlling the movement of the C-arm at an operating console, that there is the threat of a collision. Furthermore the movement of the C-arm can be halted or the speed of the movement reduced if the C-arm is approaching the fictitious envelope surface.
One disadvantage of the known device is that optical signals can easily be overlooked since the user also has to take account of other optical information communicated during the movement of the C-arm. Although acoustic signals are not as a rule missed, an acoustic signal which lasts for a longer period can drown out other important acoustic signals, for example the acoustic signals of an electrocardiograph. In addition the patient becomes restless, generally assuming that a malfunction has occurred.